1. Technical Field of the Invention
The present invention relates to microelectronics.
2. Description of Related Art
Microelectronics is conventionally based on the production of planar devices.
Using only deposition techniques, it is possible to deposit successive layers of stratiform materials, in which the chemical composition varies from one layer to the next. This gives a vertical gradient if the variations of composition from one layer to the next are fairly slight.
Doping also makes it possible to vary the composition gradually inside a layer delimited by interfaces.
All these conventional techniques cause the creation of a vertical gradient of composition, that is to say parallel to the thickness of the substrate, well-suited to the conventional fabrication methods.